Can anyone explain how the drop down menu works on the Outsider tut. In particular how does the 'MouseOver Menu' layer work?

Logic would tell me that all highlights in this layer should show, but somehow they have managed to make one rectangle to appear at a time - the mosue over instrution to this layer only appears when my text cursor is on the space between 'xara' and 'xtreame' on the second line! But surly for each line you need a seperate layer and a mouse over instruction for each line of text. I like the tidyness of their way but how did they do it?

Turan